Pillow blocks are not new per se and the prior art discloses a variety of sealing arrangements for pillow blocks. For example, the KOELSCH U.S. Pat. No. 4,881,829, shows a pillow block assembly including a seal chamber located outside the pillow block housing. More specifically, the open end of the housing (10) mounts a triple labyrinth seal (29) and a cartridge seal ring (35) is mounted in a chamber assembly (34) adjacent to the labyrinth seal. Lubricating fluid may be pumped into and out of the sealing chamber (34). The roller bearing assembly (25) is lubricated by grease supplied through a port (32) which connects to a passage (33) leading to the interior of the housing. The grease fills the housing cavity up to the labyrinth seal (29).
Thus the KOELSCH sealing arrangement is rather complex and comprised of many components. A drawback in the KOELSCH arrangement is the complexity and expense of the KOELSCH seal. Further, the KOELSCH seal is non-purgeable, which may cause a problem if the housing is overfilled with grease. Additionally, in some applications which produce thermal shaft expansion in the axial direction, it has been found that the contacting surfaces in the KOELSCH seal tend to separate and consequently there is a loss of sealing function. Moreover, by reason of the additional seal housing, the combined pillow block and seal housing require a considerable axial width which limits use of a pillow block and sealing arrangement of this type in applications where space requirements are tight.
TESKE U.S. Pat. No. 3,128,104 shows a labyrinth seal for shafts comprising a ring magnet (16) bonded to a flexible corrugated membrane (17) adhesively bonded to a flexible corrugated membrane (17) formed with a solid foot portion (18). The assembly further includes a supplementary labyrinth seal comprising disks (31) and (32).
Accordingly, the TESKE seal assembly relies on metal to metal contact and by reason of its construction and configuration cannot be used in applications where there is some amount of axial shaft expansion since shaft expansion would effectively create forces disassembling the seal. Note that in FIG. 5 of TESKE, the two rings have to be moved axially relative to one another to assemble the seal. The TESKE seal assembly requires press fits and ground surfaces to properly mount the seal to the shaft housing assembly. Further, TESKE'104 patent may be broadly described as a magnetic seal and therefore there is no pumping action associated with the seal. TESKE does not incorporate a directional aspect whereby, lubricant can flow in one direction to purge it and the seal has lubricant retention capabilities in its normal operating position. Furthermore, the TESKE seal is not purgeable.
TOOLY, U.S. Pat. No. 4,348,067, shows a pillow block housing and a seal comprising an axial face riding v-ring seal (56) which utilizes axial contact lip pressure to provide a seal at both ends of the housing. This lip seal is located externally of the housing and is therefore exposed and in this condition can be easily damaged, for example, by ultraviolet degradation or contaminants. Furthermore, the TOOLY design is not readily reversible without additional machining of the pillow block housing and requires the inclusion of additional elements, such as a washer or use of special tools to prevent the seal lip from folding under the labyrinth during assembly of the housing cap.